JP2002541490A - Radiation detector and apparatus used for surface beam radiography and method for detecting ionizing radiation - Google Patents

Abstract

(57) Abstract: A detector 64 for detecting ionizing radiation, an apparatus for surface beam radiography including such a detector, and a method for detecting ionizing radiation. The detector comprises a chamber filled with an ionizable medium, first and second electrode devices (2, 1, 18, 19) disposed in the chamber with a gap having a conversion volume (13); It comprises an electronic avalanche amplifying means (17) arranged in the chamber and at least one read element device (15) for detecting an electronic avalanche. The radiation inlet is provided such that the radiation is incident on the conversion volume between the first and second electrode devices. To clearly form an avalanche, the electronic avalanche amplification means includes a plurality of avalanche regions.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention comprises a chamber filled with an ionizable gas, first and second electrode devices provided with a gap containing a conversion and drift volume in the chamber, and a gap disposed within the gap. An ionizing radiation detector comprising: an electronic avalanche amplifying means; a readout device for detecting at least one electronic avalanche; a device used for beam radiography including such a detector; and a device for generating emitted electrons. The invention relates to a method for detecting ionizing radiation in which radiation interacts with gas atoms in a conversion and drift volume filled with gas.

[0002] Detectors and devices of the above type are co-pending PCT-application PCT / SE98 / 0
No. 1873, which is incorporated herein by reference. The detector described in that reference comprises a gas parallel plate avalanche chamber. This detector has good resolution, high X-ray detection efficiency, and is capable of counting all photons incident on the detector. This has even greater potential when processing detection signals, such as energy detection, identification of detection signals from photons in a specific energy range or photons input within a specific distance range from the anode or cathode. Can be

When this type of detector is used for surface beam radiography, that is, slit type or scanning type radiography, a high quality image can be obtained simply by irradiating a subject with only a low dose of X-ray photons. Can be provided.

Another detector and device of the above-mentioned kind belonging to the field of the invention is EP-A1-081
No. 0631.

For gas parallel plate avalanche chambers, it is believed that the anode and cathode plates need to be parallel and much effort has been made to achieve parallelism between the plates. However, the critical point is that the distance over which the electrons are avalanche amplified, ie the length of the electron avalanche, does not change at different locations in the gas parallel plate avalanche chamber. The reason is that the amplification is strongly dependent on the distance from the avalanche start point to the end point. However, avalanche anodes and cathodes have large dimensions in the plane in which they extend as compared to the distance between them. Therefore, it is very difficult and expensive to provide sufficient uniformity of the distances or gaps.

A main object of the present invention is to provide a one-dimensional detector for detecting ionizing radiation. This detector employs avalanche amplification, provides a good avalanche, provides a simple and convenient method. It can be produced cost effectively.

[0007] These and other objects are achieved by a detector according to claim l.

A radiation inlet is provided so that the radiation is incident on the conversion volume between the first and second electrode devices, and the electronic avalanche amplifying means includes at least one avalanche cathode device and at least one avalanche anode device, and includes an avalanche amplification device. A voltage is applied between the avalanche cathode device and the avalanche anode device to generate at least one electric field for use by the detector according to the invention, wherein the electronic avalanche amplification means comprises a plurality of avalanche regions. A detector is obtained which is given a length in the direction of the incident radiation in order to obtain the desired stopping power which makes it possible to detect most of the incident radiation.

[0009] This feature also provides a detector capable of extracting electrons emitted by the interaction between photons and gas atoms in a direction substantially perpendicular to the incident radiation. This makes it possible to obtain a very high positional resolution.

[0010] Furthermore, this feature provides a detector that provides good resolution and high X-ray detection efficiency and can count most of the photons incident on the detector.

[0011] A detector that provides good energy resolution for X-rays can also be obtained.

Further, it is possible to obtain a detector which can operate with a high X-ray flux without deteriorating the performance and has a long life.

[0013] The above features also provide a detector that effectively detects electromagnetic radiation and all types of radiation, including incident and elementary particles.

Apparatus used for surface beam radiography that employs avalanche amplification and comprises at least one one-dimensional detector for detecting ionizing radiation, provides good avalanche, and can be manufactured easily and cost-effectively It is also an object of the present invention to provide

[0015] These and other objects are achieved by an apparatus for surface beam radiography comprising the above detector.

By including the above-mentioned detector, an apparatus used for surface beam radiography, that is, slit type or scanning type radiography, in which a high quality image can be obtained only by irradiating a subject with a low dose of X-ray photons, is obtained. be able to.

A major part of the X-ray photons incident on the detector is detected, and a device for surface beam radiography can be obtained which further counts or integrates to obtain each pixel value of the image.

An apparatus for surface beam radiography with very little surface beam image noise caused by radiation scattered in the subject can be obtained.

An apparatus for surface beam radiography with less image noise caused by diffusion of an X-ray energy spectrum can be obtained.

It is possible to obtain an apparatus for surface beam radiography which is simple and inexpensive, has a high X-ray detection efficiency, and has a detector capable of operating with good X-ray energy resolution.

Furthermore, it is possible to obtain an apparatus for surface beam radiography provided with a detector which has a long life and a high X-ray flux without deteriorating performance.

It is also an object of the present invention to provide a method for detecting ionizing radiation that employs avalanche amplification, provides good avalanche, and can be implemented simply and inexpensively.

This and other objects are directed to a method of detecting ionizing radiation in which gas atoms and radiation interact within a gas-filled conversion and drift volume to generate emitted electrons, the method comprising: Within the first electric field, which is substantially perpendicular to the direction of the radiation, forcing an electric field into one of a plurality of regions each having a concentrated electric field to produce an electron avalanche. And the electronic avalanche is detected by readout element means.

This feature provides a way to detect most of the incident radiation.

Furthermore, this feature provides a method by which electrons emitted by the interaction between photons and gas atoms can be extracted in a direction substantially perpendicular to the incident radiation. This makes it possible to obtain a very high positional resolution.

It is possible to obtain a method that can be used with a high X-ray flux.

FIG. 1 is a sectional view of the apparatus for surface beam radiography according to the present invention in a plane perpendicular to the plane of the surface X-ray beam 9. The apparatus comprises an X-ray source 60, which generates a planar fan-shaped X-ray beam 9 together with a first elongated collimator window 61 and irradiates an object 62. The first elongated collimator window 61 can be replaced by another means for forming a plane X-ray beam, such as an X-ray diffraction mirror or an X-ray lens. The beam transmitted through the subject 62 enters the detector 64. Optionally, a narrow slit or second collimator window 10 aligned with the x-ray beam forms the entrance of the x-ray beam 9 to the detector 64. The main part of the incident X-ray photons is detected by a detector 64, which comprises a conversion and drift volume 13, and an electronic avalanche amplification means 17, wherein the X-ray photons are applied to both electrode devices 1,
2 are arranged to be incident from the side, and an electric field for drifting electrons and ions in the conversion and drift volume 13 is formed between the electrode devices.

In this example, the surface X-ray beam is a beam collimated by the collimator 61.

The detector and its operation will be further described below. The X-ray source 60, the first elongated collimator window 61, the optional collimator window 10 and the detector 64 are connected and fixed to each other by specific means 65, for example, a frame or a support 65. The radiographic device thus formed can be moved as a device for scanning a subject. As shown in FIG. 1, in a single detector system, scanning is done by a rotational movement, for example, by rotating the device about an axis through an x-ray source 60 or detector 64. The position of the axis depends on the application or application of the device, and in some applications the axis may pass through subject 62. The scan is
It can also be implemented by a moving movement in which the detector and the collimator move, or by moving the subject. In a multi-line configuration in which a large number of detectors are stacked, the scanning can be performed in various ways, which will be described later with reference to FIGS. In many cases, it is advantageous to have the device fixed and the subject moved.

The detector 64 includes a first drift electrode device serving as the cathode plate 2 and a second drift electrode device serving as the anode plate 1.
A drift electrode device is provided. These are parallel to each other and in the space between them there is a narrow gap or region 13 filled with gas, which is a conversion and drift volume,
Also, an electronic avalanche amplification means 17 is provided. A voltage is applied to the anode plate 1 and the cathode plate 2, and one or more voltages are applied to the electronic avalanche amplifier 17. As a result, a drift electric field causing drift of electrons and ions is generated in the gap 13, and an electron avalanche amplification electric field is generated in the electron avalanche amplification means 17. A reading element device 15 for detecting an electronic avalanche is provided in association with the anode plate 1. Preferably, the read element device 15 also constitutes the anode electrode. Alternatively, the read element device 15 may be formed in association with the cathode plate 2 or the electronic avalanche amplifier 17. Further, it may be formed on an anode or cathode plate separated from an anode or cathode electrode by a dielectric layer or a substrate. In this case, the anode or cathode electrode needs to be translucent to the induced pulse, and is formed in a strip or pad shape, for example. 3 and 4 show different realizable read element devices 15.

As is apparent from the figure, the X-ray to be detected enters the detector from the side and enters the conversion and drift volume 13 between the cathode plate 2 and the anode plate 1. The X-rays preferably enter the detector from a direction parallel to the cathode plate 2 and the anode plate 1 and enter the detector through an elongated slit or collimator window 10. In this manner, a detector can be readily fabricated having an interaction path long enough for the major portions of the incident X-ray photons to interact and be detected. If a collimator is used, the collimator is preferably arranged such that the thin surface beam is incident on a detector close to the electronic avalanche amplification means 17 and is preferably arranged parallel thereto.

The gap or region 13 is filled with a gas, for example a mixture of 90% krypton and 10% carbon dioxide, or for example 80% xenon and 20%
Of carbon dioxide. The gas can be pressurized, preferably in the range of 1-20 atm. Accordingly, the detector comprises an airtight housing 91 having a slit-shaped entrance window 92. The X-ray beam 9 enters the detector from this window. This window is made of a radiation-transparent material, for example Mylar or thin aluminum foil. This specifically detects the side incident beam of the gas avalanche chamber 64 as compared to the gas avalanche chamber previously used and designed for incident radiation normal to the anode and cathode plates and requiring a wide window. This is an advantageous additional effect of the present invention. The window can thus be made narrower, thus reducing the number of X-ray photons absorbed in the window.

In operation, the incident X-rays 9, if installed, the electronic avalanche amplification means 1
It enters the detector through any elongated slit or collimator window 10 close to 7 and passes through the gas volume, preferably in a direction parallel to the electronic avalanche amplification means 17. Each X-ray photon produces a primary ionizing electron ion pair in the gas as a result of its interaction with gas atoms. This generation is due to the photoelectric effect, the Compton effect, or the Auger effect. Each generated primary electron 11 loses kinetic energy by interacting with another gas atom, and further generates an electron ion pair (secondary ionization electron ion pair). Generally, in this process, one 20 keV X-ray photon produces hundreds to thousands of secondary ionized electron ion pairs. The secondary ionized electrons 16 (along with the primary ionized electrons 11) drift toward the electron avalanche amplification means 17 due to the electric field in the conversion and drift volume 13. When electrons enter the region of the electron avalanche amplifier 17 where the lines of electric force converge, avalanche amplification is performed. This is described further below.

The movement of avalanche electrons and ions induces an electric signal for electronic avalanche detection in the readout device 15. These signals are detected in connection with the electronic avalanche amplifying means 17, the cathode plate 2 or the anode plate 1, or a combination of two or more of the above areas. The signal is further amplified and processed by the readout circuit 14 to accurately measure the location of the X-ray photon interaction and, if necessary, the X-ray photon energy.

FIG. 2 a is a partially enlarged view of FIG. 1 of a detector according to a first embodiment of the invention.
FIG. 2 is a sectional view taken along line II-II of FIG. As is apparent from this figure, the cathode plate 2 includes a dielectric substrate 6 serving as a cathode electrode and a conductor layer 5. The anode 1 is composed of a dielectric substrate 3 serving as an anode electrode and a conductor layer 4. Between the gap 13 and the anode 1, an electronic avalanche amplifier 17 is arranged. The amplifying means 17 includes an avalanche amplification cathode 18 and an avalanche amplification anode 1 separated by a dielectric 24.
9 is provided. As shown, this may be a gas or a solid substrate 24 carrying a cathode 18 and an anode 19. As is clear from the figure, the anode electrodes 4 and 1
9 is formed of the same conductor. A voltage is applied between the cathode 18 and the anode 19 by the DC power supply 7, and an extremely strong electric field is formed in the avalanche amplification region 25.
The avalanche region 25 is formed between or around the ends of the avalanche cathode 18 facing each other. In this region, a concentrated electric field is generated by an applied voltage. DC power supply 7 is also connected to cathode electrode 5 and anode electrode 4 (19). The applied voltage is selected so that a weak electric field or drift electric field is formed in the gap 13.
The electrons (primary and secondary electrons) emitted by the interaction in the conversion and drift volume 13 drift to the amplification means 17 due to the drift electric field. The electrons enter a very strong avalanche amplified electric field and are accelerated. The accelerated electrons 11, 16 are
Interacts with other gas atoms in the region 25 to generate further electron-ion pairs. These generated electrons are accelerated in the electric field, interact with newer gas atoms, and generate more electron-ion pairs. This process continues while the electrons move in the avalanche region toward the anode 19, and an electron avalanche occurs. The electrons that have left the avalanche region drift toward the anode 19. If the electric field is strong enough, the electron avalanche can continue up to the anode 19.

The avalanche region 25, if any, is formed by the cathode 18 and the openings or channels in the dielectric substrate 24. The openings or channels may be circular, as viewed from above, or may be a longitudinal continuum extending across the ends of the substrate 24 and, if present, between the cathodes 18. If the openings or channels are circular when viewed from above, they are arranged side by side and each row of openings or channels has a plurality of circular openings or channels. A plurality of elongated openings or channels or rows of circular channels are formed adjacent to each other and parallel to each other or parallel to the incident X-rays. Alternatively, the openings or channels can be arranged in another pattern.

The anode electrodes 4, 19 also form the read element 20 in the form of a strip provided in connection with the opening or channel forming the avalanche region 25. Preferably, one strip is arranged for each opening or channel or row of openings or channels. The strip can be divided along its length, one section being provided in the form of a pad in each circular opening or channel or a plurality of openings or channels. The strips and sections, if any, are electrically insulated from each other. Each detector electrode element or strip or section is preferably separately connected to the processing circuit 14. Alternatively, the read element may be arranged on the back surface of the substrate (the side opposite to the side of the anode electrodes 4 and 19). In this case, the anode electrodes 4, 19 need to be translucent to the induced pulse, for example in the form of a strip or a pad. 3 and 4 show different possible read element arrangements 15.

As one example, the elongate channel may have a width in the range of 0.01-1 mm, and the circular channel may have a diameter in the range of 0.01-1 mm. In addition, dielectric 2
The thickness of 4 (the distance between the avalanche cathode 18 and the anode 19) is in the range of 0.01-1 mm.

Alternatively, the dielectric substrates 3, 6 can be replaced by conductor layers, and the conductor layers 5, 4 can be replaced by anticorrosive carriers, for example silicon monoxide, conductive glass or diamond. In this case, the dielectric layer or carrier, if arranged in connection with the drift electrode device, is preferably arranged between the conductor layer and the read element 20.

FIG. 2 b is a cross-sectional view of the detector according to the second embodiment of the present invention, taken along line II-II of FIG. This embodiment shows that the anode electrodes 4 and 19 are formed of different conductors separated by dielectrics, which can be solid or gaseous, and that the openings or channels are also within the avalanche anode electrode 19. It differs from the embodiment of FIG. 2a in that it is formed. The avalanche amplification anode 19 is connected to the DC power supply 7. If the dielectric between anode electrodes 4 and 19 is solid, openings or channels are included through the dielectric. The opening or the channel basically corresponds to the opening or the channel forming the avalanche region 25. An electric field is formed between the anode electrodes 4 and 19. This electric field can be a drift electric field, ie a weak electric field, or an avalanche amplified electric field, ie a very strong electric field. 3 and 4 show different possible read element arrangements 15.

FIG. 2 c is a cross-sectional view taken along line II-II of FIG. 1 of a detector according to a third specific embodiment of the present invention. The detector includes the cathode 2, the anode 1, and the avalanche amplification means 17, as described above. A gap 13 which is a conversion and drift volume is provided between the cathode 2 and the avalanche amplification means 17. The gap 13 is filled with gas, and the cathode 2 is formed as described above. The drift anode 1 is provided on the back surface of a dielectric substrate 26, for example, a glass substrate. On the other hand, on the front surface of the substrate 26, an avalanche amplification cathode 18 and an anode 19 strip are provided. Cathode 18 and anode 1
The 9 strips are conductor strips and are connected to the DC power supply 7 to form a concentrated electric field, that is, an avalanche amplification electric field, in each region between the cathode strip 18 and the anode 19 strip. The anode 1 and the cathode 2 are also connected to a DC power supply 7. The applied voltage is selected so that a weak electric field and a drift electric field are formed in the entire gap 13. Alternatively, the dielectric substrate 26 may be replaced with a gas. In that case, the anode and the cathode are supported, for example, at their respective ends.

Preferably, the avalanche anode strip 19 also forms the read element 20 and is further connected to the processing circuit 14. Instead, avalanche cathode strip 1
8 forms a read element or is formed together with the anode strip 19. Alternatively, the anode electrode 1 may be composed of strips that can be divided and are insulated from each other. These strips may be formed only with readout elements or with anode and / or cathode strips. The strip functioning as the anode / cathode and the readout element is connected to the DC power supply 7 and the processing circuit 14 by a connection method suitable for separation. As a further alternative, the cathode strip 18 and / or the anode strip 19 are formed by a base conductor layer covered by a resistive top layer, for example of silicon monoxide, conductive glass or diamond. This reduces the output of sparks that can be generated in the gas by a strong electric field. In yet another readout strip device, the readout strip 20 is arranged parallel below the avalanche anode strip 19. And the readout strip 20 is made slightly wider than the avalanche anode strip 19. If they are placed under the anode 1, the anode electrode must be translucent to the induced pulse, for example in the form of a strip or pad. In a further alternative, the anode 1 may be omitted since the required electric field is formed by the cathode electrodes 5, 18 and the anode electrode 19.

As an example, the glass substrate is about 0.1-5 mm thick. In addition, the conductive cathode strip has a width of approximately 20-1000 μm, and the conductive anode strip has a width of approximately 10-200 μm. The pitch is approximately 50-2000 μm. The cathode and anode can be divided into segments along the direction in which they extend.

In operation, X-ray photons are incident on a space 13 in the detector of FIG. 2 c essentially parallel to the avalanche cathode 18 and anode 19 strips. Within the conversion and drift volume 13, incident X-ray photons are absorbed and electron-ion pairs are generated as described above. A group of primary and secondary electrons resulting from the interaction by one X-ray photon drift toward the avalanche amplification means 17. The electrons are incident on a gas-filled region between the anode strip and the cathode strip, that is, a very strong electric field in the avalanche amplification region. In a strong electric field, the electrons start electron avalanche. As a result, the number of electrons gathering on the anode strip is several orders of magnitude higher than the number of primary and secondary electrons (so-called gas amplification). One advantage of this embodiment is that each electronic avalanche elicits only one signal on almost one anode element or essentially one detector electrode element. Therefore, the position resolution on one coordinate is determined by the pitch.

In the above embodiment, different positions of the detector electrode device have been described. There are many variations on this, for example, one or more detector electrode devices can be provided in different orientations of the strips or segments, adjacent to each other, or at separate locations.

FIG. 3 shows a possible configuration of the detector electrode devices 4, 5, 15. The electrode arrangements 4, 5, 15 are formed of strips 20 'and operate not only as detector electrodes but also as anode or cathode electrodes. A number of strips 20 'are arranged side by side and extend at each location in a direction parallel to the incident X-ray photons. The strip is
They are electrically insulated from each other and are formed on the substrate with a space 23 therebetween. The strip is formed by a photolithographic method or an electroforming method. The width of space 23 and strip 20 'is tailored to the particular detector to obtain the desired (optimal) resolution. For example, in the embodiment of FIG. 2a, the strip 20 'is located below an opening or channel or row of openings or channels and has a width essentially equal to or somewhat wider than the opening or channel. This is valid both when the detector electrode device is located away from the anode electrode 4 and when the detector electrode device is also constituted by the anode electrode 4.

Each strip 20 ′ is connected to the processing circuit 14 by an individual signal conductor 22,
The signal of each strip is preferably processed separately. Where the anode or cathode electrode constitutes the detector electrode, the signal conductor 22 also connects each strip to the high voltage DC power supply 7 in a connection suitable for separation.

As can be seen, strip 20 ′ and spacing 23 are targeted at x-ray source 60, and the strip is widened along the direction of the incident x-ray photons.
This configuration compensates for parallax.

The electrode device shown in FIG. 3 is preferably an anode, but alternatively or in conjunction with the cathode, the cathode may have the above configuration. If the detector electrode device 15 is a separate segment, the anode electrode 4 may be formed as a single electrode without strips and spacing. The same is true for the cathode electrode or the anode electrode when the other is constituted by a detector electrode device. However, if the detector electrode device is located on the substrate opposite the cathode or anode electrode,
The anode or cathode electrode is translucent to the induced pulse and is formed, for example, as a strip or pad.

FIG. 4 shows another configuration of the electrode. The strip is divided into segments 21 and is electrically insulated from each other. Preferably, a small spacing extending perpendicular to the incident X-rays is provided between each segment 21 of the respective strip. Each segment is connected to the processing circuit 14 by an individual signal conductor 22, and the signals of each segment are preferably processed individually. As shown in FIG. 3, if the anode or cathode electrode comprises a detector electrode, the signal conductors 22 also connect their respective strips to the high voltage DC power supply 7.

Since the statistically high energy X-ray photons pass through a longer path in the gas than the low energy X-ray photons and cause primary ionization, when measuring the energy of each X-ray photon, Can be used. The position of the X-ray photon interaction and the energy of each X-ray photon can be detected by the electrodes. Statistical techniques can recover the spectrum of incident photons with high energy resolution. For example, EL Ko
sarev et al. Nucl. Instr and methods 208 (1983) 637, and GF Karabadj
See ak et al., Nucl. Instr and methods 217 (1983) 56.

In general, in all embodiments, each incident X-ray photon produces one stimulation pulse at one (or more) detector electrode element. This pulse is processed by the processing circuit. The circuit ultimately shapes the pulses and accumulates or counts the pulses from each strip (pad or pad set) representing one pixel. The pulses can also be processed to provide a measure of energy to each pixel.

When the detector electrode is on the cathode side, the area of the induced signal is wider (in the direction perpendicular to the direction of incidence of the X-ray photons) than on the anode side. Therefore, it is preferable to perform signal measurement in the processing circuit.

FIG. 5 is a schematic diagram of one embodiment of a stacked plurality of inventive detectors 64 of the present invention. According to the present embodiment, multi-line scanning can be realized, so that not only the scanning time but also the entire scanning distance can be reduced. The apparatus of the present embodiment includes an X-ray source 60, which forms a large number of planar fan-shaped X-ray beams 9 with a large number of collimator windows 61 and irradiates an object 62. The beam transmitted through the subject 62 is X
Arbitrarily incident on the individually stacked detectors 64 through a number of second collimator windows 10 aligned with the line beam. The first collimator window 61 is
Arranged in the first rigid structure 66 and optionally the second collimator window 10
It is located in the second rigid structure 67 mounted on the detector 64 or individually on the detector.

An X-ray source 60, a rigid structure 66, and possible structures 67 each comprising a collimator window 61, 10, and a stacked detector 64 fixed to one another are provided with specific means 65,
For example, they are connected and fixed to each other by a frame or a support 65. The radiographic device thus formed can be moved as a single device and can scan a subject. In this multi-line configuration, as described above, scanning is performed by a transverse motion perpendicular to the x-ray beam. If the radiographic device is fixed, it is preferable to move the subject.

Another advantage of using a stacked configuration compared to a large volume single gas detector is the reduction of background noise caused by X-ray photon scattering within the subject 62. These scattered X-ray photons traveling in a direction that is not parallel to the incident X-ray beam pass through the anode and cathode plates and, upon entering such a chamber, produce a spurious signal or signal at one of the other detectors 64 stacked. Produces avalanche. This reduction is achieved by significant absorption of (scattered) X-ray photons in the anode and cathode plates, or in the material of the collimator 67.

As shown in FIG. 6, this background noise is further reduced by providing a thin absorbing plate 68 between the stacked detectors 64. The stacked detector is similar to that of FIG. 5, except that a thin sheet of absorbent material is provided between each adjacent detector 64.
These absorbing plates or sheets can be made of a high atomic number material such as, for example, tungsten.

As another example of all embodiments, the electric field in the conversion and drift gap (volume) can be kept strong enough to cause electronic avalanche, and thus can be used in pre-amplification mode.

In all embodiments, generally, the gas volume is very small and the ions are immediately removed, so that the space charge is low or not accumulated. This allows for a high rate of operation.

Also, in all embodiments, in general, the operating voltage can be reduced by reducing the distance, which reduces the potential for sparks, which is desirable for electrons.

In the embodiment, the convergence of the electric lines of force is preferable for suppressing the formation of the streamer. This reduces the risk of sparks.

As another example, the gap or region 13 may include an ionizable medium, such as a liquid or solid medium, instead of the gaseous medium. The solid or liquid medium may be a conversion and drift volume and an electronic avalanche volume.

The ionizable liquid medium is, for example, TME (trimethylethane) or TMP (
Trimethylpentane) or other ionizable liquid media having similar properties.

The solid medium which can be ionized can be, for example, a semiconductor material, for example silicon or germanium. If the ionizable medium is a solid, the housing 91 around the detector may be omitted.

A detector using an ionizable solid or liquid medium can be much thinner,
Further, the resolution of the image of the subject detected by the detector is less affected by the direction of the incident X-rays than a similar gas detector.

Although the electric field is preferably in a region where avalanche amplification occurs, the present invention is effective even in a low voltage region that is not sufficient to cause an electronic avalanche when an ionizable solid or liquid medium is used in the detector. is there.

Although the present invention has been described in connection with a number of embodiments, it will be understood that various modifications can be made without departing from the spirit and view of the invention as defined by the appended claims. Should be. For example, the voltage can be applied in other ways as long as the electric field is formed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an overall image of an apparatus for surface beam radiography according to a general embodiment of the present invention.

FIG. 2a shows a partially enlarged view of the detector according to the first embodiment of the invention, II in FIG. 1;
It is sectional drawing in the -II line.

FIG. 2b shows a partially enlarged view of the detector according to the second embodiment of the invention, II in FIG. 1;
It is sectional drawing in the -II line.

FIG. 2c shows a partially enlarged view of the detector according to the third embodiment of the invention, II in FIG. 1;
It is sectional drawing in the -II line.

FIG. 3 is a schematic diagram of an embodiment of an electrode formed by an X-ray source and a readout strip.

FIG. 4 is a plan view of a second embodiment of an electrode formed by an X-ray source and a segmented readout strip.

FIG. 5 is a cross-sectional view of an embodiment of the present invention having a stacked detector.

FIG. 6 is a cross-sectional view of a further embodiment of the present invention having a stacked detector.

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Claims (35)

[Claims] 1. A chamber filled with an ionizable gas, first and second electrode devices disposed in the chamber with a gap including a conversion and drift volume therebetween, and disposed in the gap. An electron avalanche amplifying means, and a readout element device for detecting at least one electronic avalanche, wherein a radiation entrance is provided such that radiation enters a conversion volume between the first and second electrode devices. The electronic avalanche amplification means includes at least one avalanche cathode device and at least one avalanche anode device, and a voltage is applied between the avalanche cathode device and the avalanche anode device to generate at least one electric field for avalanche amplification. Wherein the electronic avalanche amplification means includes a plurality of avalanche regions. Ionizing radiation detector. 2. The detector according to claim 1, wherein said electronic avalanche amplification means includes an electric field concentration means. 3. The detector according to claim 2, wherein said electric field concentrating means includes an avalanche cathode provided with an opening or a hole. 4. The surface of a dielectric substrate forming at least one limited surface of a region for local avalanche amplification between said at least one avalanche cathode and said at least one avalanche anode. The detector according to claim 1, wherein: 5. The at least one avalanche cathode and the at least one avalanche cathode.
5. A method according to claim 1, wherein two avalanche anodes are formed on the first surface of the dielectric substrate with a gap, said gap forming a limited surface of the area for local avalanche amplification. The detector according to claim 1. 6. The detector according to claim 1, wherein the at least one avalanche cathode and the at least one avalanche anode include a conductive strip. 7. The detector according to claim 5, wherein a plurality of avalanche cathodes and anodes are provided alternately on the substrate. 8. The detector according to claim 7, wherein the avalanche cathode and the avalanche anode have conductive strips whose longitudinal ends are substantially parallel to the incident radiation. 9. The at least one avalanche cathode is formed on a first side of a dielectric substrate, the at least one avalanche anode is formed on a second side of the dielectric substrate, and at least one channel is formed on the dielectric substrate. The detector according to claim 4, wherein the at least one avalanche cathode and the at least one avalanche anode are disposed on the dielectric substrate, and the at least one avalanche anode forms a wall of the at least one channel. 10. The at least one avalanche cathode is formed on a first side of a dielectric substrate, the at least one avalanche anode is formed on a second side of the dielectric substrate, and at least one channel is formed on the dielectric substrate. The detector according to claim 4, wherein the detector is disposed on at least one avalanche cathode, the dielectric substrate, and the at least one avalanche anode. 11. The detector according to claim 9, wherein the at least one channel has an essentially circular cross section. 12. The method according to claim 9, wherein the at least one channel has a substantially square cross section and extends between two opposite ends of the dielectric substrate. Detector. 13. The detector according to claim 1, wherein the readout element comprises an elongate strip having a longitudinal end parallel to the incident radiation. 14. The detector according to claim 1, wherein the readout element comprises an elongated strip having a longitudinal end perpendicular to the incident radiation. 15. The device according to claim 1, wherein the first electrode device is a drift cathode, the second electrode device is a drift anode, and the read element is arranged between the drift anode and the avalanche anode. Detector according to paragraph. 16. The device according to claim 1, wherein the first electrode device is a drift cathode, the second electrode device is a drift anode, and the drift anode is arranged between the readout element and the avalanche anode. The detector according to claim 1. 17. The device according to claim 1, wherein the first electrode device is a drift cathode, the second electrode device is a drift anode, and the drift cathode is arranged between the readout element and the avalanche cathode. The detector according to claim 1. 18. The detector according to claim 1, wherein the read element also forms a first drift electrode device. 19. The detector according to claim 1, wherein the read element also forms a second drift electrode device. 20. The detector according to claim 1, wherein the readout element also forms an avalanche anode device. 21. The detector according to claim 1, wherein a plurality of strip-shaped readout elements are arranged below the avalanche region. 22. The detector according to claim 1, wherein a pad-like read element is arranged below each avalanche region or a series of avalanche regions. 23. A thin slit or collimator window, wherein the radiation is
The detector according to any one of the preceding claims, wherein the detector is arranged in association with an entrance so as to be incident near the electrode device. 24. The method according to claim 1, wherein a narrow slit or a collimator window is arranged in relation to the entrance so that the radiation is incident close to the avalanche cathode. The described detector. 25. The detector according to claim 1, wherein the chamber is filled with an ionizable liquid or solid instead of the ionizable gas. 26. An apparatus for surface beam radiography comprising an X-ray source and means for forming a substantially planar X-ray beam between said X-ray source and a subject. An apparatus for surface beam radiography, comprising the detector according to claim 1. 27. A means for stacking a number of detectors to form a detector, wherein a means for forming a substantially planar X-ray beam is disposed at each detector, said means being provided between said X-ray source and a subject. Wherein the X-ray source, the means for forming the substantially planar X-ray beam and the detection device are fixed to each other to form a device used for scanning an object. 27. The device of claim 26, wherein 28. The apparatus according to claim 27, wherein an absorption plate is disposed between the detectors for absorbing scattered X-ray photons. 29. Apparatus according to claim 26, wherein a narrow slit or collimator window is arranged on the side of each detector facing the X-ray source. 30. A method for detecting ionizing radiation in which radiation interacts with gas atoms in a conversion and drift volume filled with a gas to generate emitted electrons, wherein the electrons are coupled to a first electric field in the conversion drift volume. Wherein the electric field is substantially perpendicular to the direction of the radiation, the electric field forcing electrons into one of a plurality of regions each having a concentrated electric field to cause electron avalanche; A method wherein an electronic avalanche is detected by the read element means. 31. The method according to claim 30, wherein the region having a concentrated electric field is formed by electric field concentrating means. 32. The method according to claim 30, wherein the region having the concentrated electric field is formed by an avalanche cathode provided with openings or holes. 33. The method according to claim 30, wherein the signals generated by the electronic avalanche in each region having a concentrated electric field are detected individually. 34. The method according to claim 30, wherein the signals generated by the electronic avalanche in a series of regions having a concentrated electric field are detected individually. 35. The method according to claim 30, wherein the radiation interacts with atoms belonging to a liquid or solid material instead of gaseous atoms.